The present exemplary embodiments relate to tools and techniques for viewing documents on display screens. People often print physical copies of documents in order to visually examine content located in different places within a document, or to compare visual content located in different documents. The same is true of other electronic source files, such as PDF files, slideshow presentation files, electronic drawing files, web page content, etc. Different content portions in a given printed page can then be brought together by folding the paper or in other ways. For example, certain bits of content may be physically cut from a paper printout, and the bits can be laid out together on a table for examination and comparison. Conventional software tools provide some limited capability for comparing disparate portions of a source document or of different documents, such as by opening separate windows next to each other, each containing an instance of the entire document, but the user must navigate the display of each window to a corresponding portion to be compared. Certain word processors and spreadsheet programs provide means for placing different portions of a file in proximity, such as by creating a “split screen” view of a document, or by selectively freezing and/or hiding specific rows or columns of a spreadsheet file. U.S. Pat. No. 7,200,615 to Eschbach et al., assigned to Xerox Corporation, incorporated herein by reference, provides techniques for presenting spreadsheets and other documents on client-side devices with limited resources and tiny display screen area, with a split-bar stitched into a composite view of the user's current viewpoint. However, such tools and multiple window techniques may not be available on all user devices, such as smart phones, etc. Moreover, available tools do not allow direct comparison of arbitrary portions of two or more commonly used file formats, and do not allow side-by-side comparison of specific portions of a digital file that are far apart or are not aligned. Accordingly, a need remains for improved tools and techniques for comparing multiple disparate portions of one or more source files to facilitate a user visually comparing select portions without opening multiple windows in a user device and without printing out the files.